First off, I don’t have an Apple TV or any device that support Google TV. I have a Roku and it’s fine for now.
On to my idea: One of the main functions platforms often perform is to make it easier to find things. One of the more sophisticated ways of doing this is through a recommendation engine (think Pandora, Netflix, Amazon’s User who bought that also bought this recommendation). A use case: Whenever something is played on an Apple TV (let’s say a Netflix movie), Apple should be listening for what music is being played (think Shazam) and offer it up for purchase when you are done watching that movie. Google could do the same thing, even by listening to commercials. Google Music is a bit different than iTunes, but it would still be valuable. Clearly Apple has a direct sale that could result from this capability via iTunes.